hi there !
sorry, but i've never heard about a direct stimulation of Tc cells via
MHC II on Th cells.
the following way is the most investigated:
a pre Tc cell, expressing TcR all the time gets it first stimulation by
antigen presented on MHC I molecules. normal cells expressing MHC I and
possibly APCc (macrophages...) are capable of this step. recognition on
Tc cell side via the TcR.
now the tc cells are prestimulated and rising levels of Il-2, IFNg and
Il-6 are leading to proliferation and cytotoxic aggression to all cells
presenting the above antigen processed on MHC I.
only the origin of the above interleukins is likely in many cases Th !!
another story is that Th cells don't release these interleukins without
preliminary stimulation via MHC II !!
nevertheless, if anybody has ideas how Th cells are able to stimulate Tc's
directly I'm very interested. we are studying autoimmune disease, Th cell
mediated - a link to the Tc's would be a great thing...
I appreciate any other opinion !!
--------------------------------------------------------------------------------
Tom Pasternak e-mail: ugn4501 at aberdeen.ac.uk
University of Aberdeen / SCOTLAND lab-tel: (224) 681818-53905
Ophthalmology / Immunology lab-fax: (224) 685158
ABERDEEN
AB9 2ZD
U.K.
================================================================================